Dietary changes of Mediterranean Shags<i>Phalacrocorax aristotelis desmarestii</i>between the breeding and post-breeding seasons in the upper Adriatic Sea

Cosolo, Mauro; Privileggi, Nicoletta; Cimador, Barbara; Sponza, Stefano

doi:10.1080/00063657.2011.603290

Cited by 14 publications

(18 citation statements)

References 45 publications

(72 reference statements)

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“…Theory suggests that diet diversifies when predominant prey become scarce and/or lessen in profitability (Stephens & Krebs 1986), and empirical evidence in other seabird studies supports this (Croxall et al 1999, Cosolo et al 2011. Shags exploit a wide range of prey (Barrett 1991, Velando & Freire 1999, Lilliendahl & Solmundsson 2006, Cosolo et al 2011, Michelot et al 2017) and can adjust their foraging behaviour in response to a change in availability of different prey types within their foraging range (Wanless et al 1998, Daunt et al 2007, Bogdanova et al 2014, Michelot et al 2017.…”

Section: Diet Trendsmentioning

confidence: 91%

“…Previous analyses of shag diet from the early period of this study demonstrated that, during the breeding season, this population consisted of sandeel specialists (Harris & Wanless 1991. However, diet varies substantially across the species' range, including large numbers of Gadidae and Gobiidae taken by some populations, suggesting that shags adopt a flexible foraging strategy to exploit available prey (Steven 1933, Furness 1982, Cosolo et al 2011, Hillersøy & Lo rentsen 2012. Such flexibility could have resulted in a change in diet composition and diversity over the past 3 decades if sandeels have become scarcer and/or lessened in energetic value relative to alternative prey, or non-sandeel prey have become more common and/or increased in energetic value.…”

Section: Introductionmentioning

confidence: 99%

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From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

Howells¹,

Burthe²,

Green³

et al. 2017

Mar. Ecol. Prog. Ser.

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Long-term changes in climate are affecting the abundance, distribution and phenology of species across all trophic levels. Short-term climate variability is also having a profound impact on species and trophic interactions. Crucially, species will experience long-and short-term variation simultaneously, and both are predicted to change, yet studies tend to focus on only one of these temporal scales. Apex predators are sensitive to long-term climate-driven changes in prey populations and short-term effects of weather on prey availability, both of which could result in changes of diet. We investigated temporal trends and effects of long-and short-term environmental variability on chick diet composition in a North Sea population of European shags Phalacrocorax aristotelis between 1985 and 2014. The proportion of their principal prey, lesser sandeel Ammodytes marinus, declined from 0.99 (1985) to 0.51 (2014), and estimated sandeel size declined from 104.5 to 92.0 mm. Concurrently, diet diversification increased from 1.32 (1985) to 11.05 (2014) prey types yr −1 , including members of the families Pholidae, Callionymidae and Gadidae. The relative proportion of adult to juvenile sandeel was greater following low sea surface temperatures (SSTs) in the previous year. In contrast, the proportion of Pholidae and prey richness were higher following high SST in the previous year. Within a season, the proportion of sandeel in the diet was lower on days with higher wind speeds. Crucially, our results showed that diet diversification was linked to trends in SST. Thus, predicted changes in climate means and variability may have important implications for diet composition of European shags in the future, with potential consequences for population dynamics.

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Section: Diet Trendsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

Howells¹,

Burthe²,

Green³

et al. 2017

Mar. Ecol. Prog. Ser.

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“…Assignation of fish to a particular functional group is somewhat controversial, increasing discrepancies with regard to considering shags pelagic, demersal or benthic feeders. Nevertheless, most authors agree on the importance of the seabed in provisioning this bird, and also its foraging flexibility (Wanless et al 1991b, Cosolo et al 2011. Our study reveals that shags prey preferably on small pelagic fish and cormorants on demersal fish.…”

Section: Discussionmentioning

confidence: 74%

Competition for food between the Mediterranean shag, the great cormorant and artisanal fisheries: a case study

et al. 2018

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Summary:The Mediterranean shag (Phalacrocorax aristotelis desmarestii) and the great cormorant (P. carbo sinensis) are syntopic birds in an area encompassing Grosa Island and the Mar Menor coastal lagoon (SE Spain, western Mediterranean) during the breeding season of the former and the wintering period of the latter. Diet composition of both birds was studied through pellet analysis and otolith identification. Competition for fish resources between these two seabirds and with local artisanal fisheries was assessed. Shags preyed preferentially on small pelagic fish, and great cormorants mainly consumed demersal fish. Shag diet consisted of marine fish strictly, but great cormorant fed in all the available environments in the study area, including marine, transitional (coastal lagoon) and freshwater reservoirs. The great dissimilarity observed between shag and great cormorant diet composition showed no competition between them. The low shag population density and fishing effort in their foraging area suggested no competition with fisheries. Conversely, great cormorant population density in the study area was very high, and they foraged on fish of high commercial value. However, competition between great cormorant and artisanal fisheries only affected some of the less abundant species fished.Keywords: competition; fisheries; great cormorant; otolith; predation; shag; syntopy.Competencia por el alimento entre el cormorán moñudo, el cormorán grande y la pesca artesanal: un caso de estudio Resumen: El cormorán moñudo (Phalacrocorax aristotelis desmarestii) y el cormorán grande (P. carbo sinensis) son especies sintópicas en el entorno de Isla Grosa y la laguna costera del Mar Menor (SE de España, Mediterráneo occidental) durante la época de reproducción del primero que coincide con la invernada del segundo. Se estudia la composición de la dieta de ambas especies mediante la identificación de otolitos en sus egagrópilas, y se evalúa la competencia entre ambas especies y con la pesca artesanal local. El cormorán moñudo se alimentó mayoritariamente de pequeños peces pelágicos, y el cormorán grande consumió principalmente peces demersales. La dieta del cormorán moñudo consistió estrictamente de peces marinos, mientras que el cormorán grande capturó peces en los diferentes ambientes acuáticos de la zona de estudio, incluyendo especies marinas, de lagunas costeras e incluso de embalses de agua dulce. La gran disimilitud observada entre la composición de la dieta de ambas aves nos indica que no existe competencia por el alimento entre ellas. Asimismo, la baja densidad poblacional de cormorán moñudo y su esfuerzo pesquero en la zona de estudio tampoco demuestran competencia con la pesca artesanal local. Por el contrario, la abundancia de cormorán grande en la zona de estudio es muy alta, y se alimentaron principalmente de especies de alto valor comercial para los pescadores locales. No obstante, solo se observó competencia con la pesca artesanal local por alguna especie de pez de las menos abundantemente capturadas por los pes...

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“…The species is largely sedentary although some populations, as the Adriatic, are migratory (Sponza, Cosolo, & Kralj, 2013) and feed on fish predominantly near the seabed (Cosolo, Privileggi, Cimador, & Sponza, 2011;Sponza, Cimador, Cosolo, & Ferrero, 2010), but may eventually exploit trawling discards. Gillnets and fish traps, especially when permanently located close to the sea shore, have been suggested to be responsible for killing significant numbers of shags (Gallo-Orsi, 2003;Zydelis et al, 2013).…”

Section: Study Speciesmentioning

confidence: 99%

“…We then use these demographic estimates and information on other parameters to build age-structured stochastic population models with which to assess population viability (Bakker & Doak, 2008;Morris & Doak, 2002 recently been suggested that it should be treated as a separate species (Sangster et al, 2012) (but see . Previous work showed low survival rates not expected in a long-lived species (Genovart, Sanz-Aguilar, et al, 2013) The species is largely sedentary although some populations, as the Adriatic, are migratory (Sponza, Cosolo, & Kralj, 2013) and feed on fish predominantly near the seabed (Cosolo, Privileggi, Cimador, & Sponza, 2011;Sponza, Cimador, Cosolo, & Ferrero, 2010), but may eventually exploit trawling discards. Previous work showed low survival rates not expected in a long-lived species (Genovart, Sanz-Aguilar, et al, 2013) The species is largely sedentary although some populations, as the Adriatic, are migratory (Sponza, Cosolo, & Kralj, 2013) and feed on fish predominantly near the seabed (Cosolo, Privileggi, Cimador, & Sponza, 2011;Sponza, Cimador, Cosolo, & Ferrero, 2010), but may eventually exploit trawling discards.…”

Section: Introductionmentioning

confidence: 97%

Varying demographic impacts of different fisheries on three Mediterranean seabird species

Genovart

Doak

Igual

et al. 2017

Global Change Biology

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Fisheries have an enormous economic importance, but reconciling their socio-economic features with the conservation and sustainability of marine ecosystems presents major challenges. Bycatch mortality from fisheries is clearly among the most serious global threats for marine ecosystems, affecting a wide range of top predators. Recent estimates report ca. 200,000 seabirds killed annually by bycatch in European waters. However, there is an urgent need to rigorously estimate actual mortality rates and quantify effects of bycatch on populations. The Mediterranean Sea is one of the most impacted regions. Here, we estimate for the first time both bycatch mortality rates and their population-level effects on three endemic and vulnerable Mediterranean taxa: Scopoli's shearwater, Mediterranean shag, and Audouin's gull, that die in different types of fishing gears: longlines, gillnets and sport trolling, respectively. We use multi-event capture-recapture modelling to estimate crucial demographic parameters, including the probabilities of dying in different fishing gears. We then build stochastic demography models to forecast the viability of the populations under different management scenarios. Longline bycatch was particularly severe for adults of Scopoli's shearwaters and Audouin's gulls (ca. 28% and 23% of total mortality, respectively) and also for immature gulls (ca. 90% of mortality). Gillnets had a lower impact, but were still responsible for ca. 9% of juvenile mortality on shags, whereas sport trolling only slightly influenced total mortality in gulls. Bycatch mortality has high population-level impacts in all three species, with shearwaters having the highest extinction risk under current mortality rates. Different life-history traits and compensatory demographic mechanisms between the three species are probably influencing the different bycatch impact: for shearwaters, urgent conservation actions are required to ensure the viability of their populations. Results will be very useful for guiding future seabird conservation policies and moving towards an ecosystem-based approach to sustainable fisheries management.

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Dietary changes of Mediterranean ShagsPhalacrocorax aristotelis desmarestiibetween the breeding and post-breeding seasons in the upper Adriatic Sea

Cited by 14 publications

References 45 publications

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

Competition for food between the Mediterranean shag, the great cormorant and artisanal fisheries: a case study

Varying demographic impacts of different fisheries on three Mediterranean seabird species

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